In the case of a known articulated tracked vehicle unit comprising a front and a rear carriage which are pivotally connected together and each of which has two track support assemblies of essentially similar construction for driving an endless drive track or tread which runs around the track-support assembly includes a carrier, a so-called saddle beam, on which there is journalled a drive wheel unit, a plurality of carrier wheel units and a track tensioning wheel unit. The tensioning wheel unit on the track support assembly is positioned furthest to the rear of the saddle beam and is also required to function as a tensioning wheel, i.e. is required to be positionable in the longitudinal direction of the track support assembly so as to enable track tension to be adjusted, and also to function as a track carrier wheel so as to therewith minimize the pressure exerted by the track support assembly on the underlying ground surface. The carrier wheel units and the tensioning wheel unit are pivotally mounted on the saddle beam by means of pendular arms that are pretensioned or biassed by means of torsion springs such as to enable respective wheel units to move resiliently over ground irregularities. The pendular arm of the known tensioning wheel unit is shorter than the pendular arm of the carrier wheel units, meaning that the suspension of the tensioning wheel unit will be more rigid, i.e. less resilient, than the spring suspension of the carrier wheel units. This limits passenger and driver comfort when driving over rough country and also results in an unfavourable distribution of the pressure exerted on the ground beneath the tracks. Furthermore, a tensioning wheel unit that includes a relatively short pendular arm will result in wide variations in track stretch as the tensioning wheel unit springs back and forth (up and down). This is because the pendular arm of the tensioning wheel unit has relatively pronounced movement in the longitudinal direction of the track as the unit springs inwardly.